FRAGMENTATION OF A CARBON NUCLEUS INTO 3 ALPHA-PARTICLES AT AN INCIDENT MOMENTUM OF 4.2 GEV C PER NUCLEON IN A PROPANE BUBBLE-CHAMBER/

The coherent dissociation C-12 --> 3 alpha on a carbon target at an in cident momentum of 4.2 GeV/c per nucleon is observed, and its cross se ction is estimated. The dependence of the cross section on the target mass number is investigated. The momentum characteristics and correlat ions of a particles from coherent dissociation as observed in the labo ratory system and in the rest frame of the nucleus undergoing fragment ation are compared with those for incoherent transitions and those for heavier target nuclei. The mechanism of the dissociation C-12 --> 3 a lpha is shown to depend strongly on the target mass number and on the character of nucleus-nucleus interaction.